This invention relates to an electronic postage scale and, more particularly, to such a scale wherein postal rate data is stored in various sections of a memory, each section being substantially associated with a class of shipment for a parcel to a destination zone, and each memory section being constituted by plural addressable storage locations whereat the postal rate data is stored and which are addressable as a function of the weight of a parcel and the particular destination zone thereof. The present invention is further concerned with various control features incorporated into such a postage scale whereby the possibility of displaying an improper or erroneous postal rate is significantly minimized. The present invention is additionally concerned with an electronic postage scale of relatively simple construction, reduced cost and which takes full advantage of digital circuitry which is available in integrated circuit form.
Generally, in computing the requisite postage for a parcel to be mailed to a desired destination, such postage is not only dependent on the weight of the parcel but, in addition, depends upon the particular destination zone and the class of shipment that is desired. Typically, the classes of shipment which are available are individually associated with a unique postage rate. As an example, such classes of shipment are priority, UPS intrastate and interstate, parcel post, book rate and blue label.
Prior to the advent of automatic postage calculating devices, an individual would determine the proper postage by firt weighing the parcel to be shipped and, once the weight of that parcel has been determined, a reference table associated with the selected class of shipment was consulted and the indicated postage for the desired destination zone was recorded. A comparison of postage rates for each class of shipment required that the individual refer to each reference table and record the corresponding postage obtained therefrom. It was fully appreciated that this technique of computing postage was not only time consuming but was subject to various errors that inadvertently could occur during the normal usage of such reference tables.
Accordingly, the introduction of automatic postage scales and calculating devices evidently met a definite need. One such prior art automatic postage scale is disclosed in U.S. Pat. No. 3,738,438. This postage scale uses digital techniques to automatically provide an indication of the postage required for a selected class of shipment to a desired destination zone in accordance with the weight of the parcel to be shipped. The postage data for each class of shipment and destination zone are provided as coded perforations in an adjustable postage code roll. That is, the postage codes are arranged on the roll in a plurality of groups, each group representing the postage rates for a particular combination of distance zone and class of shipment. An operator advances the roll to select the proper rate group. When the proper rate group is selected, it consists of a plurality of sets of further codes representing the postage for various parcel weights in the selected rate group. The particular data set is detected in accordance with the weight of the parcel and the postage represented by that data set is read out and displayed.
The use of such as encoded postage data roll requires that an operator, or auxiliary automatic apparatus, advance the roll until the proper rate group representing a predetermined class of shipment and a desired destination zone is obtained. This, of course, requires careful supervision by the operator and further requires the use of a bulky data roll that occupies space which could otherwise be advantageously used. Hence, the total time required to determine the requisite postage for a parcel, although significantly reduced from previous mechanical postage scales which relied upon the operator consultation of rate charts, can be still further reduced.
Another example of a prior art electronic postage scale is described in U.S. Pat. No. 3,692,988. In this sytem, a digital representation of parcel weight is produced and an optical drum is used to store postal rate data. Addressable portions of this optical drum are selected as a function of the parcel weight and a selected destination. Once addressed, the data stored at this location in the optical drum is read out and can be used for display or for automatically operating a suitable postage meter device.
Yet another prior art postage scale is described in U.S. Pat. No. 3,635,297. In this postage scale, suitable selector switches are provided to enable an operator to select a particular class of shipment and to key in the ZIP code information of the parcel destination, corresponding to the destination zone. A read only memory is divided into sections which may correspond, generally, with the available classes of shipment. In a memory section, postal rates are stored at individually addressable locations, the postal rate at each such location being a function of the parcel weight and the destination zone.
The prior art postage scales which have been briefly described hereinabove by way of example, suffer from the common disadvantage in that they are not provided with satisfactory or sufficient control apparatus. That is, these scales will provide a postal weight display for many instances wherein insufficient information has been provided to permit a proper rate to be determined. For example, while some prior art postage scales advantageously display a changing postal rate caused by the movement of the scale platform when a parcel initially is placed thereon or is removed therefrom, many of these scales will provide an unintelligible display for the case wherein the scale platform returns and then passes through its initial reference position. This display, which can be though of as a "negative weight" display, is best prevented so as to avoid possible confusion of an operator or attendant of the postage scale. Also, some prior art postage scales will provide a postal rate display once a suitable class of shipment and destination zone for the parcel have been determined, even though the parcel has not yet been weighed. This display for "zero weight" often can be confusing; and it is best to prevent a postal rate display until a finite parcel weight has been detected. In still other prior art postage scales, a postal rate will be displayed even though all of the information necessary for determining such a postal rate has not yet been entered into the scale. For example, if the class of shipment or destination zone of the parcel has not been entered, some of these scales nevertheless will provide a postal rate indication. Since this indication is, essentially, meaningless, it is best to prevent such a display until all of the requisite data has been entered.
Another disadvantage attending such prior art postage scales is that they do not adequately exploit the availability of relatively inexpensive integrated circuit components. For example, for those scales which utilize an electronic or magnetic memory device for storing postal rate information, such memories generally are of the type which store an entire digital word representing the complete weight information at each addressable location. Since the postal rate usually is in terms of dollars and cents, each of which may be a two-digit decimal number, such a digital word may be, for example, a 16-bit word. Memories which must store 16-bit words generally are quite expensive. This expense can be significantly reduced if the size of the digital word is decreased, and if time-sharing, or multiplexing, techniques are used to read postal rate data out of the memory. For example, a substantial savings can be realized if the memory device need only store 8-bit digital words, and if each addressed location encompasses two of such words which are read out in time-sharing format.